ok, first thing in a year from now you will have algee growing all over your liner and you will never see it anyway. To anwer your ? about rocks inside some are ok but i dont recomend alot because it gives detritus and parisights a place to live. So if you want to keep a healthy and happy pond then the fewer the better. plus If you ever have to treat for sickness it is alot easier to do when filling your pond use a gallons meter so you can treat your fish. they will get sick. plus you will go through new pond synd.